Is sourdough bread low FODMAP? Wheat, spelt and the real answer

Is sourdough low FODMAP? The honest answer is: it depends. It depends on the flour, and it depends on how long the dough ferments. Monash University has tested specific types of traditionally made sourdough and lists low FODMAP servings for them. A loaf with "sourdough" on the bag is a different question.

This article explains why fermentation matters, what Monash lists, and how to read a sourdough label in the supermarket.

Why fermentation changes the FODMAP content

Wheat, rye and barley contain fructans, a fermentable carbohydrate from the FODMAP family. Fructans are the reason regular wheat bread is high FODMAP at a typical serve. Gluten is a different molecule, and it is not a FODMAP. Our article on FODMAPs vs gluten explains that difference in detail.

A sourdough starter is a live culture of wild yeasts and lactic acid bacteria. When a baker mixes the starter with flour and water, these microorganisms feed on the carbohydrates in the flour. Fructans are part of that food. According to the Monash University blog on sourdough, the yeast and bacteria start to degrade the FODMAPs during fermentation, and traditional sourdough dough typically proves for more than 12 hours.

So time is the key ingredient. A long, slow fermentation gives the culture more time to consume fructans. The finished loaf can therefore contain less fructan than the same flour baked quickly with commercial yeast.

The grain matters too. Monash describes spelt as an ancient species of wheat with a notably lower fructan content than modern wheat. Spelt flour plus a long fermentation gives you two advantages at once.

What Monash University has tested

Monash publishes its test results in the Monash FODMAP app, and serving sizes can change when foods are retested. Use the app for current figures. At the time of writing, Monash's public information includes these points:

• Traditional spelt sourdough. The Monash blog post Wheat and a low FODMAP diet lists 2 slices of spelt sourdough bread as a low FODMAP option. Monash also notes that this applies to spelt bread made with very traditional sourdough methods, not to every spelt product (Spelt products and FODMAPs).
• Traditional white wheat sourdough. Monash has also tested a traditionally made white wheat sourdough, and its app lists a low FODMAP serving of 2 slices.
• Oat sourdough. The same Monash wheat article lists 1 slice of oat sourdough bread.

Two details are easy to miss. First, these serves are for the specific breads Monash tested. Second, a larger serve of the same bread may contain more fructans. Our guide to FODMAP serving sizes explains why the dose matters as much as the food.

The supermarket sourdough problem

Here is where it gets tricky. The word "sourdough" on a bag does not guarantee a traditional method. Some loaves on the shelf follow it. Many others use a short fermentation with baker's yeast, and some add a dried sourdough powder or an acid for the sour flavour.

A label lists ingredients, not process. It does not tell you how many hours the dough fermented. Two loaves with almost the same ingredient list can have a very different fructan content.

So treat a supermarket sourdough as a product that may need further checking, not as a declared low FODMAP bread. A few clues on the ingredient list can help:

• Sourdough or starter near the top of the list suggests the culture does real work in the dough.
• Yeast plus "sourdough flavouring" or dried sourdough suggests a fast process. The sour taste may come without the long fermentation.
• The flour type. Spelt is the grain with Monash test results behind it. Rye sourdough and wholemeal wheat loaves are different products, so the spelt result does not transfer to them.
• Added FODMAP ingredients. Inulin, chicory root, honey or dried fruit add FODMAPs regardless of the fermentation.

Bakeries that make traditional sourdough can often tell you the fermentation time if you ask. Some breads also carry a low FODMAP certification from a testing programme, which gives you a tested result for that exact product. Our bread aisle guide lists more label points to watch.

Other low FODMAP bread options

Sourdough is not the only route during the elimination phase.

Gluten-free bread is often an easy option, because many loaves use rice, corn or other flours that are lower in fructans. But gluten-free is not automatically low FODMAP. Gluten is not a FODMAP, and some gluten-free loaves contain inulin, chicory root, honey, apple juice concentrate or legume flours. Check the full list.

Wheat starch is not wheat flour. Processing removes much of the fructan-containing part of the grain, so wheat starch can appear in low FODMAP products. Wheat flour keeps the fructans of the grain. Our article on hidden FODMAPs on labels covers this distinction and other wheat ingredients.

If you prefer to bake at home, our pizza loaf cake is a savoury loaf made with buckwheat flakes instead of wheat dough.

Remember that the elimination phase is temporary. During reintroduction, you test fructans and find your own tolerance, ideally with a FODMAP-trained dietitian. Many people find that they tolerate some regular bread, at least in smaller amounts.

Get tested for coeliac disease first

Sourdough made from wheat or spelt still contains gluten. Fermentation reduces fructans, it does not make a loaf suitable for people with coeliac disease.

If you think gluten or wheat may be causing symptoms and you have not been tested for coeliac disease, speak to your doctor before removing gluten from your diet. Coeliac testing is most reliable while you are still regularly eating gluten.

Let Belly Buddy help with the label

Scan the ingredient list of a loaf and Belly Buddy helps you identify declared ingredients that may affect its FODMAP profile, such as wheat flour, rye, inulin, chicory root or honey.

Belly Buddy reads the ingredient list. It cannot see how the bread was made or how long the dough fermented. For a sourdough, use the result together with what you know about the bakery and its process. Our rating method explains how Belly Buddy analyses ingredients.

Belly Buddy is not affiliated with or endorsed by Monash University. Our FODMAP information is informed by publicly available scientific sources, including research from Monash University.

Sources

• Monash University: Sourdough processing and FODMAPs
• Monash University: Wheat and a low FODMAP diet
• Monash University: Spelt products and FODMAPs